An LED (i.e., light emitting diode) is a semiconductor device capable of converting electric energy to visible light. An LED can directly convert electricity to light. LED lighting can provide advantages including energy conservation, environmental protection, controllable lighting, strong practicability, high stability, short response time, and long operation lifetime. LED lighting has been widely used in various lighting areas for low-carbon lifestyle.
Current LED dimming technology is often based on a SCR type dimmer (also referred to as a SCR dimmer). In current LED dimming technology, the output of a SCR dimmer may be connected to a rectifier circuit and the output of the rectifier circuit may be connected to the bus line voltage. One terminal of a primary side of the transformer may be connected to the bus line voltage, and the other terminal may be connected to the CS (i.e., current sampling) pin of an IC (i.e., integrated circuit) such that a DC voltage signal may be used as an input to the CS end of the IC. The IC may be used to correct the primary power factor of the transformer. By adjusting or changing the value of the DC voltage signal, the IC may change the peak value of the primary current of the transformer connected to the IC. Thus, the SCR dimmer can change/dim the light of the LED.
However, when the value of the bus line voltage is at wave trough (e.g., bottom or minimum value), the value of the switch-off threshold may become considerably small, which is because the value of the switch-off threshold in the power factor correction circuit is proportional to the value of the bus line voltage, the value of the switch-off threshold may be close to zero when the value of the bus line voltage is close to zero. When the value of the switch-off threshold is close to zero, the voltage offset value on the current sampling (CS) end of the IC may often be greater than the value of the switch-off threshold. As a result, the IC may stop functioning, and the transition between the latching current to the holding current of the SCR dimmer may not be continuous current. The SCR dimmer may be shut off unexpectedly, and the LED may have undesired flashing/strobing light.